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The original light saver

The Original Light Saver
A new laser device puts an end to denture wars

December 2002

by Aileen Salinas

Rodney Phoenix, D.D.S., has made hundreds of removable partial dentures in his lifetime and taught hundreds of dental students to do the same. But after watching both students and professionals struggle with the process, he knew he could find a better way. So Dr. Phoenix, who is an associate professor in the department of prosthodontics, invented what he calls a planar light beam orientation device. The technology makes it faster and easier to create a more precise prosthetic.

Creating a removable partial denture depends heavily on a technicianís ability to accurately reproduce the tilt a dentist used during the design process. The tilt is the basis for recording the exact measurements required to make a denture.

To start, a dentist creates a cast of a patientís mouth and then places precise color-coded directions on the cast. The directions serve as a blueprint for the technician. They indicate the exact shape, size and dimensions of the partial denture components and indicate where they should be positioned on existing teeth. The blueprint includes orientation marks that technicians use to align it properly. Finding the proper position is an essential step in creating partial dentures.

"Design and fabrication of accurate removable partial dentures requires that we record the precise orientation (position) of a cast. We place marks on the cast so a technician can accurately reorient the cast to a prescribed position," Dr. Phoenix said. "And that is absolutely essential. If technicians canít recreate the desired tilt, then we encounter some difficulties."

Traditionally, technicians lock the cast into a device called a surveying table, then use a dental surveyor to re-establish the desired tilt. The tilt of the cast is adjusted until orientation marks line up on a single horizontal plane. It doesnít usually happen on the first try. If the orientation marks are not lined up properly, the cast must be changed.

"Itís a matter of trial and error," Dr. Phoenix said. "The technician has to keep moving the castís position. It might be too low on one side so the cast has to be adjusted. Then it could be too high in the front, but too low elsewhere. As a result, the technician has to adjust the tilt a little and check the alignment again." The process continues until all the orientation marks finally line up with the surveyor on the horizontal plane. "And unless youíre relatively experienced, that could take a while. It can be really frustrating for a student, too," Dr. Phoenix said.

The planar light beam orientation device enables technicians to find the castís original position almost immediately. The device looks like a flashlight and attaches to the vertical arm of a dental surveyor. A small, optically-pure metallic cone sits in the path of the light beam. As the laser beam strikes the cone, the light is reflected horizontally. "The device projects a horizontal beam through 360 degrees," Dr. Phoenix said. Since the user can line up all orientation marks at the same time, the trial and error part of orienting a cast is eliminated.

"Most students are visually adept. When using the device, they generally say, ĎWow, this is simple. All I need to do is move the cast this way, and Iím done,í" Dr. Phoenix said. "In a teaching environment, students can easily see and understand the position of the horizontal plane with this device. Otherwise, itís a little more abstract and often frustrating."

Using Dr. Phoenixís recently patented device, technicians can get relatively close to the exact position on the first try. Fine-tuning the castís positioning is easy from this point because the beam shines all the way around the cast, allowing a technician to line up the orientation marks at once. "Instead of making all those movements over and over again, now itís essentially a matter of setting up the cast and checking the position," Dr. Phoenix said. "Because you can see where the orientation marks are in relation tothe laser, you can very quickly and accurately locate the castsí intended position. Itís become a pretty simple task. And now youíre ready to go on to the next step in partial denture fabrication."

The deviceís simple design and practical function could save technicians about five minutes per prosthesis. "In large laboratories, that time can add up very quickly," Dr. Phoenix said. In the end, technicians can make prosthetics more accurately and more efficiently, and students grasp the concept faster and can provide accurate information to technicians. As a result, patients get an improved service and a better fitting prosthesis without the potential complications resulting from misaligned casts.

The device currently is used at the Health Science Center, but Dr. Phoenix plans to market it to other institutions and laboratories.

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Updated 7/30/14